Shutter drive mechanism

ABSTRACT

Variable shutter mechanism for a motion picture camera has the main shutter blade mounted on the forward end of the main shutter shaft and driven in fixed phase relation to the intermittent mechanism, and the variable shutter blade journaled coaxially to the rear of the main blade, leaving the forward end of the main shaft available for driving connection to other apparatus. A reflex shutter may be mounted on an oblique axis forward of the main shutter mechanism, the reflex shutter shaft being coupled directly to the main shaft, preferably via a constant speed universal joint.

United States Patent Inventor George A. Mitchell 687 Prospect Crescent,Pasadena, Calif. 91103 Appl. No 23,298 Filed Mar. 27, 1970 Patented Aug.10, 1971 SHUTTER DRIVE MECHANISM 2 Claims, 5 Drawing Figs. 11.8. CI352/206 Int. Cl. G03b 9/8 Field of Search 352/205, 206, 208,214, 216,217, 219

References Cited UNITED STATES PATENTS 1,173,706 2/1916 Carleton .L352/216 2,012,352 8/1935 Rusting 2,858,750 11/1958 Farinet,lr.....

Primary Examiner S. Clement Swisher Attorney --Charlton M. LewisABSTRACT: Variable shutter mechanism for a motion picture camera has themain shutter blade mounted on the forward end of the main shutter shaftand driven in fixed phase relation to the intermittent mechanism, andthe variable shutter blade journaled coaxially to the rear of the mainblade, leaving the forward end of the main shaft available for drivingconnection to other apparatus. A reflex shutter may be mounted on anoblique axis forward of the main shutter mechanism, the reflex shuttershaft being coupled directly to the main shaft, preferably via aconstant speed universaljoint.

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SHUTTER DRIVE MECHANISM This invention has to do generally with motionpicture shutters, and concerns more particularly drive mechanism forrotary shutters which comprise two shutter members that are mutuallyadjustable to vary the exposure time, and which may include reflex meansfor illuminating an optical finder during the periods of film movement.

Although shutter arrangements of that general type are well known, thedrive mechanisms which have been previously proposed tend to be undulycomplex, are difficult to construct with adequate strength and accuracy,or suffer from other practical disadvantages.

The present invention provides mechanism for mounting and driving rotaryshutters of the described type which can be constructed economically,which is inherently rugged and accurate, and which is sufficientlycompact to avoid interfering with the optical system of the camera andwith the intermittent mechanism for advancing the film.

A well-known type of variable shutter employs a main shaft which carriesthe rearmost one of the two shutter members and is coupled by suitablegearing to the intermittent mechanism, the forward shutter member beingcarried by a shaft of relatively small diameter that is journaledcoaxially in a bore extending the entire length of the main shaft. Suchmechanism places the differential coupling between the two shuttermembers at the opposite end of the main shaft, where it is readilyaccessible and where space can be made available. However, it isdifficult to design the inner shaft with sufficient strength andrigidity to give fully satisfactory performance.

In accordance with the present invention the forward member of thevariable shutter is mounted directly on the main shaft. The rearmostmember is carried by a sleeve that surrounds the main shaft coaxially inrotatable relation to it. The drive connection between that sleeve andthe main shaft is made via a differential mechanism which typicallycomprises a parallel countershaft geared directly to the sleeve andgeared to the main shaft through a phase adjusting mechanism such as apair of spiral gears of which one is splined on its shaft for axialmovement to vary the angular relation between the two shutter members.

The present invention provides improved drive mechanism for a reflexshutter that is journaled on an axis inclined at about 45 to the opticalaxisof the camera objective lens. The usual relatively complex gearingby which such a reflex shutter has previously been driven is replaced,in accordance with the present invention, by a simple universal joint ofconstant speed type, having one member mounted coaxially on the mainshaft and the other member mounted coaxially on the inclined shaft ofthe reflex shutter. When the main shutter is driven in the manner thathas been described, the forward end of the main shaft is available forsuch coupling to the reflex shutter. Due to the inherent ruggedness ofthe main shaft, the added load of the reflex shutter does not involveany structural problems. The universal joint mentioned above can bereplaced, if desired, by suitable gearing or other coupling mechanism.

A full understanding of the invention, and of its further objects andadvantages, will be had from the following description of illustrativemechanism for carrying it out. The particulars of that description, andof the accompanying drawings which form a part of it, are intended onlyas illustration and not as a limitation upon the scope of the invention.

In the drawings:

FIG. 1 is a somewhat schematic horizontal section representing anillustrative embodiment of the invention in a motion picture camera;

FIG. 2 is a vertical section taken generally on line 2-2 of FIG. 1, butdeveloped as indicated by line 2-2 of FIG. 3;

FIG. 3 is a section in the plane ofline 3-3 of FIG. 2;

FIG. 4 is a front elevation; and

FIG. 5 is a detail showing a portion of FIG. 1 at enlarged scale.

In the drawings the mainframe or housing of the camera is omitted forclarity of illustration, and it is understood that all the shaftbearings and other elements to be described are suitably mounted on sucha frame. The objective lens is indicated in fragmentary form at 10, withoptical axis- 12, and forms an image on the film 14. Film 14 is guidedfor intermittent movement in a direction normal to the plane of FIG. 1through a conventional film gate, indicated schematically at 15 with thefilm aperture 16.

The main shutter shaft 20 is journaled by the bearings 21 and 22 on theshaft axis 24, which is parallel to optical axis 12. Shaft 20 istypically driven via the gears 25 and 26 from the drive shaft 30. Thatshaft is journaled on the housing by bearings indicated at 32, is drivenby a suitable motor via the pulley 33, and typically drives directly theintermittent mechanism 34. The film advancing claw of intermittentmechanism 34 is indicated schematically at 36, and acts in conventionalmanner to advance film 14 intermittently through the film, gate.Registration pins may be provided for defining the film position duringits rest periods. The constant speed film sprocket 38 is typicallydriven by the gearing 39 from main shutter shaft 20, supplying film fromthe supply reel to the intermittent, and from the intermittent to thetakeup reel via respective film loops in conventional manner.

Light from lens 10 is cut off from film 14 during periods of filmmovement by shutter mechanism which comprises the main shutter member40, rigidly mounted on shaft 20. That shutter member preferably has onlya single vane 42, which typically extends through an angle sufficient tocover the film aperture throughout each period of film movement. Vane 42is preferably dynamically balanced, as by the counterweight indicated at44. For some purposes it may be preferred to employ a shutter with twovanes and driven at half the speed of the intermittent mechanism.

In the present structure the effective aperture of the shutter is madevariable by means of the second shutter member 50, which is mountedcoaxially with shutter member 40 and normally rotates with it, but isangularly adjustable to vary the shutter opening. Member 50 is rigidlymounted on the sleeve 53, which is freely rotatable on main shaft 20forward of hearing 22 and carries the gear 55. The rotational positionof shutter member 50 relative to shaft 20 is controlled by suitabledifferential mechanism through which sleeve 53 is driven from main shaft20. A particularly satisfactory form of differential mechanism comprisesthe countershaft 60, which is journaled by the bearings 62 on thecounteraxis 61 parallel to main axis 24. The gear 64 is rigidly mountedon countershaft 60 and continuously engages gear 55, coupling thecountershaft to shutter 50 in definite mutual speed and phaserelationship. The spiral gear 66 is mounted on countershaft 60 for freeaxial movement but in fixed rotational relation by the spline structure67. The axial position of gear 66 on the countershaft is controlled bythe yoke mechanism 68, which slides on the fixed rod 65 under manualcontrol, indicated schematically as the handle 69. Gear 66 continuouslyengages the spiral gear 70 on main shaft 20, the latter gear beingtypically formed by cutting gear teeth directly in that shaft. Gears 66and 70 thus couple main shaft 20 and countershaft 67 for rotation atnormally fixed relative speed but with mutual phase relationship that isvariable in response to axial movement of control handle 69. The pitchand dimensional relationships are selected so that control 69 can shiftthe two shutter members 40 and 50 from directly overlapping position,providing maximum shutter aperture, to a position in which the shutteraperture is either relatively small, producing minimum availableexposure time, or is zero, producing complete closure of the shutter.

A particular advantage of the described shutter and drive mechanism isthat the forward end of main shaft 20 is accessible in front of theshutter structure for connection to any further mechanism that is to bedriven in timed relation to the shutter and to intermittent movement 34.When the movable shutter member is placed forward of the fixed shuttermember, as in many previous variable shutter mechanisms, no

such drive connection is available. In those previous mechanisms theforward end of the main shaft is made completely inaccessible by therotating variable shutter member. Whereas connection might, in theory,be made to the variable shutter itself, the resulting drive, besides itslimited strength and accuracy, would be subjectto phase variations dueto adjustment of the variable shutter.

The present structure includes the reflex shutter 80, which is mountedwith the counterweight 87 on the shaft 82, journaled by the bearings 83on the axis 81. Reflex shutter axis 81 is inclined with respect tooptical axis 12 and main shaft axis 24 by the angle indicated in FIG. 1at 85, which is typically 45. Reflex shutter 80 is synchronized withmain shutter member 40, intercepting light that would otherwise strikevane 42. The intercepted light is specularly reflected by the opticallyplane front surface 84 of shutter 80, forming at the ground glass orreticle 91 an optical image 90 which corresponds directly to the imageon film 14. Image 90 is rendered visible as a finder image by the mirror92 and the finder optical system indicated schematically at 93.

Reflex shutter 80 on its inclined shaft 82 is illustrative of mechanismsthat can conveniently be driven from the forward end of main shaft 20.

The two shaft axes 24 and 81 intersect at the point 86, which is-spacedforwardly of main shaft and rearwardly of reflex shaft 82. Accordingly,space is available between those shafts for coupling them directly byany desired type of coupling structure. In accordance with the presentinvention, the preferred coupling structure for that purpose comprises auniversal joint of suitable type that provides constant speed ratiobetween the two connected shafts.

A particularly suitable type of constant speed universal joint isindicated at 100 and is shown best in FIG. 5. That structure comprisesthe two balls 102 and 104, each of which has two peripheral grooves 106and 108 in diametral planes at right angles to each other. The yokeformations 103 and 105 are mounted rigidly on the shafts 20 and 82 andslidingly engage the grooves 106 of the respective balls. The othergrooves 108 are slidingly engaged by yoke formations on opposite ends ofthe coupling member 110, which requires no other support. This type ofcoupling, though well known in and of itself, is remarkably well adaptedfor the present purpose by its compactness, simplicity and accuracy, andis quieter in operation than other coupling mechanisms such as bevelgears, for example.

I claim:

1. In combination with a motion picture camera having an objective lensand a film aperture mounted behind the lens on an optical axis,intermittent mechanism for moving a film intermittently past theaperture, and an optical finder; shutter mechanism which includes avariable shutter for varying the ratio of exposure time to dark time anda reflex shutter for illuminating the optical finder during the darktime; said shutter mechanism comprising a main shutter shaft journaledon a shaft axis parallel to the optical axis and rigidly carryingadjacent its forward end a front shutter member, the shaft beingdrivingly coupled to the intermittent mechanism in definite mutual speedand phase relation,

a sleeve journaled on the main shaft and rigidly carrying a rear shuttermember closely spaced rearwardly of the front shutter member,

the shutter members including respectiveshutter blades of truncatedsector form for intersecting light between the lens and the filmaperture in respective mutually parallel, closely spaced blade planesthat intersect the optical axis perpendicularly immediately forward ofthe film aperture and intersect the shaft axis at points spacedforwardly of the forward end of the shaft, and blade supports rigidlymounted on the shaft and on the sleeve, respectively, adjacent theforward ends thereof, and extending therefrom radially outward andaxially forward to the respective blade planes and rigidly carrying therespective blades, differential mechanism or driving the s eeve normallyat the same speed as the main shaft and for adjustably varying the phaserelation between the sleeve and the main shaft to vary the effectiveshutter opening,

a reflex shutter rigidly mounted on a reflex shaft journaled on an axisinclined obliquely to the optical axis, the reflex shutter includingreflective vane structure for intercepting light between the lens andsaid shutter blades and for reflecting intercepted light to the opticalfinder, shaft axis obliquely intersecting the main shaft axis at anintersec tion point that is spaced forwardly of the forward end of themain shaft and rearwardly of the rearward end of the reflex shaft, and

a constant speed universal joint drivingly interconnecting the rearwardend of the reflex shaft and the forward end of the main shaft indefinite mutual speed and phase relation, the universal joint beingpositioned essentially at said intersection point and predominantly tothe rear of said blade planes and within the enclosure described by saidblade supports.

2. Shutter mechanism as defined in claim 1, and in which said universaljoint comprises two members each having two concentric arcuate channelslying in mutually perpendicular planes,

yoke structures rigidly mounted on the forward end of the main shuttershaft and on the rearward end of the reflex shaft, respectively, andslidingly engaging channels of the respective members, and

a coupling member having two yoke structures mounted at its oppositeends in a common plane and slidingly engaging the other channels of therespective members.

1. IN combination with a motion picture camera having an objective lensand a film aperture mounted behind the lens on an optical axis,intermittent mechanism for moving a film intermittently past theaperture, and an optical finder; shutter mechanism which includes avariable shutter for varying the ratio of exposure time to dark time anda reflex shutter for illuminating the optical finder during the darktime; said shutter mechanism comprising a main shutter shaft journaledon a shaft axis parallel to the optical axis and rigidly carryingadjacent its forward end a front shutter member, the shaft beingdrivingly coupled to the intermittent mechanism in definite mutual speedand phase relation, a sleeve journaled on the main shaft and rigidlycarrying a rear shutter member closely spaced rearwardly of the frontshutter member, the shutter members including respective shutter bladesof truncated sector form for intersecting light between the lens and thefilm aperture in respective mutually parallel, closely spaced bladeplanes that intersect the optical axis perpendicularly immediatelyforward of the film aperture and intersect the shaft axis at pointsspaced forwardly of the forward end of the shaft, and blade supportsrigidly mounted on the shaft and on the sleeve, respectively, adjacentthe forward ends thereof, and extending therefrom radially outward andaxially forward to the respective blade planes and rigidly carrying therespective blades, differential mechanism for driving the sleevenormally at the same speed as the main shaft and for adjustably varyingthe phase relation between the sleeve and the main shaft to vary theeffective shutter opening, a reflex shutter rigidly mounted on a reflexshaft journaled on an axis inclined obliquely to the optical axis, thereflex shutter including reflective vane structure for interceptinglight between the lens and said shutter blades and for reflectingintercepted light to the optical finder, shaft axis obliquelyintersecting the main shaft axis at an intersection point that is spacedforwardly of the forward end of the main shaft and rearwardly of therearward end of the reflex shaft, and a constant speed universal jointdrivingly interconnecting the rearward end of the reflex shaft and theforward end of the main shaft in definite mutual speed and phaserelation, the universal joint being positioned essentially at saidintersection point and predominantly to the rear of said blade planesand within the enclosure described by said blade supports.
 2. Shuttermechanism as defined in claim 1, and in which said universal jointcomprises two members each having two concentric arcuate channels lyingin mutually perpendicular planes, yoke structures rigidly mounted on theforward end of the main shutter shaft and on the rearward end of thereflex shaft, respectively, and slidingly engaging channels of therespective members, and a coupling member having two yoke structuresmounted at its opposite ends in a common plane and slidingly engagingthe other channels of the respective members.